What is the risk of measles in individuals previously vaccinated against Measles (Rubeola)?

From the Guidelines

If you've been vaccinated against measles, your risk of contracting the disease is very low, with two doses of the MMR vaccine providing about 97% protection, as indicated by the latest recommendations from the Advisory Committee on Immunization Practices 1.

Key Points to Consider

• The measles vaccine (MMR) is highly effective in preventing measles, mumps, and rubella virus infections and their related complications 1.
• Two doses of the MMR vaccine provide about 97% protection against measles, making the risk of contracting the disease very low for vaccinated individuals.
• Even in the rare case that a vaccinated person contracts measles, the illness is typically much milder with less risk of complications compared to unvaccinated individuals.
• The vaccine works by stimulating the immune system to produce antibodies against the measles virus, creating immunological memory that allows the body to quickly recognize and fight the virus upon exposure.

Special Considerations

• If you're immunocompromised, pregnant, or have other high-risk conditions, it's essential to contact your healthcare provider immediately after exposure to measles, as you might need immune globulin (IG) treatment within 6 days of exposure for additional protection 1.
• HIV-infected persons are at increased risk for severe complications if infected with measles, and MMR vaccination is recommended for all asymptomatic HIV-infected persons who do not have evidence of severe immunosuppression 1.

Recommendations

• Maintaining high measles, mumps, and rubella vaccination coverage is crucial to prevent the spread of these diseases, especially in areas where they are endemic 1.
• Vaccinated individuals who are exposed to measles generally don't need to take additional precautions, but it's always best to consult with a healthcare provider for personalized advice.

From the Research

Risk of Measles in Vaccinated Individuals

• The risk of measles in individuals previously vaccinated against measles is a concern, as vaccine failure can occur, especially in those who have not received two doses of the measles, mumps, and rubella (MMR) vaccine 2.
• Studies have shown that two-dose measles vaccination provides long-term protection against severe cases, even after vaccine failures, with a 71% and 83% lower risk of severe measles in two-dose vaccine recipients compared to unvaccinated cases, if the time since last dose was less or more than 15 years, respectively 3.
• A significant proportion of individuals vaccinated with a single dose of MMR vaccine may have measles antibody levels below the putative level of protection, highlighting the importance of a second dose of MMR vaccine to ensure adequate protection 4.
• Even in vaccinated individuals, the risk of infection is high, but the risk of transmission is low, as seen in two case studies of modified measles in vaccinated physicians exposed to primary measles cases 5.
• Long-term immunogenicity after measles vaccine versus wild infection has been investigated, with findings suggesting that immunity after the disease is life-long, whereas the response after two doses of measles-containing vaccine declines within 10-15 years 6.

Factors Influencing Vaccine Effectiveness

• The time since last vaccination is a significant factor in determining vaccine effectiveness, with a longer time since last dose associated with a higher risk of vaccine failure 3.
• The number of vaccine doses administered is also crucial, with two-dose vaccination providing better protection against severe measles than single-dose vaccination 3, 4.
• Individual factors, such as immune response and previous exposure to measles, can also influence vaccine effectiveness 5, 6.

Implications for Public Health

• The risk of measles in vaccinated individuals highlights the need for continued monitoring of vaccine effectiveness and the importance of booster doses to maintain adequate protection 2, 6.
• Public health strategies should focus on ensuring high vaccination coverage and promoting awareness of the risks of vaccine failure to prevent outbreaks and protect vulnerable populations 3, 4.